The cause of the deadly McDonald's outbreak has been revealed

U.S. health officials have announced that the chopped fresh onions used in McDonald's restaurants are the source of the E. coli outbreak that has sickened 90 people.

The Centers for Disease Control and Prevention (CDC) stated, "Fresh chopped onions used in McDonald's Quarter Pounder and some other menu items are a likely source of this outbreak."

It was noted that the onions were supplied by Taylor Farms, which has voluntarily recalled them.

McDonald's has also removed these onions from their menus.

As a result of the outbreak, which temporarily removed these burgers from menus in restaurants across 12 states, 90 people became ill, 27 were hospitalized, and an elderly man in Colorado died.

McDonald's announced on Sunday that it would resume selling Quarter Pounders after receiving negative E. coli test results.

The E. coli bacteria causes stomach cramps, diarrhea, and vomiting that can last for three to four days. While most people recover without needing treatment, some patients can develop complications.